Humidifier and/or flow generator for CPAP device

ABSTRACT

A CPAP device includes a flow generator with a blower configured to pressurize the flow of respiratory gas. A flexible face seal is positioned at an outlet end of a blower discharge path. The flexible face seal includes an aperture and a lip curling inwardly from a perimeter of the flexible face seal. A tub configured to hold a body of water and humidify the pressurized flow of respiratory gas includes a heat conducting base plate and a side wall. The side wall has a substantially flat portion that surrounds an air inlet opening. A base supports both the flow generator and the tub and includes a floor with a heater plate. A laterally positioned guide prevents the tub from being removed from the base in a vertical direction and includes a pair of C-shaped channel portions with open sides that face each other.

CROSS-REFERENCE TO PRIORITY APPLICATION

This application is a continuation of U.S. application Ser. No.16/156,049, filed Oct. 10, 2018, now allowed, which is a continuation ofU.S. application Ser. No. 14/687,223, now U.S. Pat. No. 10,124,143,filed Apr. 15, 2015, which is a continuation of U.S. application Ser.No. 11/988,870, now U.S. Pat. No. 9,038,629, filed Jan. 16, 2008, whichis the U.S. national phase of International Application No.PCT/AU2006/001170, which designated the U.S. and claims the benefit toU.S. Provisional Application No. 60/707,948, filed Aug. 15, 2005, theentire contents of each of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a removable humidifier and/or flowgenerator for a Continuous Positive Airway Pressure (CPAP) device usedto treat sleep disordered breathing (SDB) conditions such as ObstructiveSleep Apnea (OSA).

BACKGROUND OF THE INVENTION

Domestic treatment of OSA and other SDB is usually done using a devicethat provides CPAP, e.g., nasal CPAP. A common configuration of atreatment system comprises a CPAP device and a patient interface, e.g.,a nasal mask. The nasal mask forms a sealing interface with thepatient's nasal passages in use so that the supply of air at positivepressure from the CPAP device may be delivered to the patient's airways.In this way, while the patient is wearing a nasal mask, their mouth isuncovered.

In some situations, patients “mouth breath” during sleep. When thishappens while wearing only a nasal mask, air can pass in the mask andstraight out the patient's mouth. This can lead to drying of thepatient's airway and patient discomfort. This patient discomfort can tosome extent be alleviated by the use of a humidifier placed between theCPAP device and the patient interface.

Many humidifiers are available, although the most convenient form is onethat is either integrated with or configured to be coupled to therelevant CPAP device. While passive humidifiers can provide some relief,generally a heated humidifier is required to provide sufficient moistureto the air so that patients will be comfortable. Humidifiers typicallycomprise a water tub having a capacity of several hundred milliliters, aheating element, a control to enable the level of humidification to bevaried, an air inlet to receive air from the blower, and an air outletadapted to be connected to an air delivery conduit so that thehumidified pressurized air may be passed to the patient interface.Usually, the water tub is removable from the system so that it can berefilled when necessary.

In making a humidification tub removable, there are two problems thatneed to be overcome. Firstly, there is a need for an air seal betweenthe air outlet of the flow generator and the air inlet of the humidifiertub. An air seal is important to reduce air leaks that may result in anincreased pressure drop between the air pressure generated by the flowgenerator and the air pressure delivered to the patient at the patientinterface. Secondly, for efficient humidification, there must beadequate thermal contact between the humidification tub and the heatingelement.

Commonly, humidifier tubs are attached either directly to a humidifiercontrol base or to a system base or cradle that facilitates the correctassembly of the flow generator with the humidifier. Generally, thehumidifier control base or the system base or cradle comprises a heatingplate that contacts the base of the humidifier tub to facilitate heatingof the water within the humidifier tub. Commonly, these base systemscomprise a spring loaded heater plate on to which the humidifier tub isattached. The spring loaded heater plate ensures good thermal contactwith the base of the humidifier tub. For example, the Fisher & PaykelHC200 system and the Respironics RemStar heated humidifier have springloaded heater plates. However, such spring loaded heater plates canprovide a friction force against insertion of the humidifier tub, whichmay make installation of the humidifier tub difficult for some users,especially older or frail users.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a seal between the humidifierinlet and flow generator outlet.

Another aspect of the invention relates to a method and apparatus forretaining a humidifier tub for use in a CPAP device, e.g., nasal CPAPdevice.

Another aspect of the invention relates to a method and apparatus forproviding good thermal contact between the humidifier tub and a heatingelement.

Another aspect of the invention relates to management of the inadvertentintroduction of water into the flow generator, e.g., by tipping oroverfilling the humidifier.

Yet another aspect of the invention relates to a CPAP device orhumidifier including a humidifier tub including a heat conducting baseplate and a cradle to support the humidifier tub in an operativeposition. The cradle includes a heater plate in communication with theheat conducting base plate of the humidifier tub in use. The cradlefurther includes a retaining mechanism to retain the humidifier tub inthe cradle. The retaining mechanism is structured to force the baseplate into engagement with the heater plate.

Another aspect of the present invention relates to a CPAP deviceincluding a cradle having a fixed heating plate; and a humidifier tubhaving a heat conducting base, the base being forcibly coupled with thefixed heating plate of the cradle upon assembly of the cradle and thehumidifier tub.

Still another aspect of the invention relates to a method for retaininga humidifier tub to a cradle, comprising providing a cradle including aretaining mechanism; moving the retaining mechanism to a first positionthat enables insertion of the humidifier tub; providing the humidifiertub to the cradle; moving the retaining mechanism to a second positionthat secures the humidifier tub in an operative position; and forcing aheat conducting base plate of the humidifier tub into engagement with aheater plate of the cradle.

Another aspect of the invention relates to a CPAP device comprising aflow generator including a flow generator outlet, a motor having a motoroutlet, a muffler chamber having an inlet coupled to the motor outletand a muffler chamber outlet in communication with a flow generatoroutlet, wherein an axis of the motor outlet is offset from an axis ofthe muffler chamber outlet and/or the flow generator outlet.

Still another aspect of the invention relates to a CPAP devicecomprising a flow generator including a flow generator outlet, a motorhaving a motor outlet, a muffler chamber having an inlet coupled to themotor outlet and a muffler chamber outlet in communication with a flowgenerator outlet, wherein said muffler chamber includes an upper partconduit portion and a lower storage portion integrally formed with thepart conduit portion.

These and other aspects, features, and advantages of this invention willbecome apparent from the following detailed description when taken inconjunction with the accompanying drawings, which are a part of thisdisclosure and which illustrate, by way of example, principles of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings facilitate an understanding of the variousembodiments of this invention. In such drawings:

FIG. 1 is a perspective view of a CPAP device according to an embodimentof the invention;

FIG. 2 is a top view of the CPAP device shown in FIG. 1;

FIG. 3 is a side view of the CPAP device shown in FIG. 1;

FIG. 4 is an end view of the CPAP device shown in FIG. 1;

FIG. 5 illustrates a blower with a seal/connector according to anembodiment of the present invention;

FIG. 6 illustrates the blower and seal/connector of FIG. 5 in anexploded position;

FIG. 7 is a cross section along section 7-7 of FIG. 5;

FIG. 8A is a cross-sectional view illustrating a seal/connectoraccording to another embodiment of the present invention;

FIGS. 8B-8C illustrate a seal/connector according to an embodiment ofthe present invention in use;

FIGS. 9-12 illustrate a cradle according to an embodiment of the presentinvention using a catch to secure the humidifier tub;

FIG. 13 illustrates a cradle according to another embodiment of thepresent invention using a sliding docking portion to secure thehumidifier tub;

FIGS. 14A, 14B, and 15 illustrate a cradle according to anotherembodiment of the present invention using a pivoting docking portion tosecure the humidifier tub;

FIG. 16 illustrates a cradle according to another embodiment of thepresent invention using a spring-biased clamping edge to secure thehumidifier tub;

FIGS. 17-22 illustrate a cradle according to another embodiment of thepresent invention using a pivotable front guard and a pivotablehumidifier retaining portion;

FIGS. 23-25 illustrate a cradle according to another embodiment of thepresent invention using a front guard and at least two pressure pads;

FIG. 26 illustrates a humidifier tub secured to the cradle shown inFIGS. 23-25, the humidifier tub engaged with the seal/connector shown inFIGS. 5-7;

FIG. 27 is a cross-sectional view through the humidifier tub and cradleshown in FIG. 26;

FIG. 28 is an exploded view of a flow generator according to anembodiment of the present invention;

FIG. 29 is a schematic drawing illustrating the general architecture ofa portion of a flow generator according to an embodiment of the presentinvention; and

FIG. 30 is a schematic exploded view of a portion of a flow generatoraccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

1. CPAP Device

FIGS. 1-4 illustrate a CPAP device 10 according to an embodiment of thepresent invention. As illustrated, the CPAP device 10 includes a flowgenerator 20 and a humidifier 30 adapted to be coupled to the flowgenerator 20.

The humidifier may be connected to the flow generator using loop-backpower and communication cables between the humidifier and the flowgenerator. In an alternative, the humidifier and the flow generator maycommunicate using a fiber optic or infrared communication system betweenthe flow generator and the humidifier. This system may detect thepresence of the humidifier tub and provide communication and powerbetween the devices via transmitters and receivers.

2. Humidifier

The humidifier 30 includes a tub or (humidifier tub) 50 having a baseplate 52 sealed to the bottom of the tub 50 and a heater element thatmay be formed as part of a cradle (or cradle unit) unit 40 (see FIG. 9).The heater element may also be formed as an integral part of the baseplate or otherwise separate from the cradle. The tub 50 includes aninlet 54 adapted to be in fluid communication with (i.e. not necessarilydirectly) the outlet 24 of the flow generator 20, and an outlet 56adapted to be connected to an air delivery conduit. The air deliveryconduit includes one end coupled to the outlet 56 of the tub 50 and anopposite end coupled to a patient interface. The patient interfacecomfortably engages the patient's face and provides a seal. The patientinterface may have any suitable configuration as is known in the art,e.g., full-face mask, nasal mask, oro-nasal mask, mouth mask, nasalprongs, etc.

The tub 50 and base plate 52 define a chamber that is adapted to receivea volume of water, e.g., several hundred milliliters. The inlet 54 andthe outlet 56 are both in communication with the chamber. In use, asupply of pressurized air from the flow generator 20 enters the inlet 54of the tub 50 and collects moisture through contact with the waterwithin the tub 50 before continuing on to the outlet 56 and to thepatient via the air delivery conduit.

As best shown in FIG. 2, the tub 50 may include a curved baffle 15adjacent the outlet end of the inlet 54 to smoothly change the directionof the air flow by gently guiding the air flow around the tub 50 whilelimiting the loss of pressure. Also, the base plate 52 may be in theform of a heat conducting base plate. Specifically, the base plate 52may be formed of a heat conducting material, e.g., aluminum sheet. Inaddition, as best shown in FIG. 23, the tub 50 may include upstandinggenerally planar side walls 102 and a rear wall 112. The tub 50 may alsoinclude a shoulder 104 extending horizontally outwards from a lowerportion of each upstanding generally planar side wall 102 of thehumidifier tub. Each shoulder 104 may include a main portion 106 and aramped portion 108. The main portion 106 may have a substantially levelupper surface, while an upper surface of the ramped portion 108 maytaper down toward the rear wall 112 of the humidifier tub 50.

In an embodiment, the humidifier 30 and tub 50 may be structured such asthe humidifier and tub described in U.S. Patent Application No.60/707,949, entitled “Humidifier Tub For CPAP Device”, filed Aug. 15,2005, the contents of which are incorporated in its entirety byreference herein. Also, in an embodiment, the flow generator 20 may bestructured and controlled such as the flow generator described in U.S.Patent Application No. 60/707,951, entitled “Low Cost CPAP FlowGenerator and Humidifier Assembly”, filed Aug. 15, 2005, the contents ofwhich are incorporated in its entirety by reference herein.

3. Seal Between Humidifier and Flow Generator

FIGS. 5-7 illustrates a connector 60 according to an embodiment of thepresent invention. The connector 60 interconnects the outlet 24 of theflow generator 20 and the inlet 54 of the tub 50. Moreover, theconnector 60 provides a pressure-activated or ‘self-energizing’ faceseal that provides a seal between the flow generator 20 and the tub 50.The seal accommodates misalignment and manufacturing tolerances asdescribed below.

As illustrated, the connector 60 provides a channel 62 (FIG. 7) todeliver pressurized air from the flow generator 20 to the humidifier tub50. In the illustrated embodiment, the connector 60 is removablyattached to the flow generator 20 and is structured to sealingly engagewith the inlet 54 of the tub 50.

As best shown in FIG. 7, the connector 60 includes two components thatare coupled to one another. Specifically, the connector 60 includes afirm frame attaching portion 64 and a flexible sealing portion 66. Thefirm frame attaching portion 64 is preferably constructed of a plasticmaterial and includes an attachment structure that enables secureattachment to the outlet 24 of the flow generator 20. For example, theattachment structure may be in the form of a snap-fit clip that includesone or more protrusions 68 adapted to engage within a correspondinggroove 70 provided in the outlet 24 with a snap fit, as shown in FIG. 7.However, the attachment structure may have other suitableconfigurations.

The flexible sealing portion 66 comprises a face seal (or bellows-typeconforming face seal) 72 preferably made from silicone or other similarmaterial that does not provide problems with creep in use. Thebellows-type conforming face seal 72 comprises an aperture 74 that isadapted to abut the inlet 54 of the humidifier tub 50. The flexiblesealing portion 66 further includes an internal sealing element 76,e.g., wiper seal, that independently seals to the outlet 24 of the flowgenerator 20 to prevent air leakage through the connection between theflow generator 20 and the humidifier 30. Any means of providing a sealbetween the flow generator 20 and humidifier 30 is encompassed withinthe scope of the invention. For example, the internal sealing element 76may be in the form of a compression sealing ridge or a wiper seal. Theflexible sealing portion 66 is constructed such that it preferably doesnot have any split lines (from the tooling) on the outer sealing facethat may interfere with obtaining a satisfactory pressure seal.

In addition, the flexible sealing portion 66 includes an interlockingstructure that is structured to interlockingly engage a complementaryinterlocking structure provided on the firm frame attaching portion 64.In the illustrated embodiment, the sealing portion 66 includes a groove78 that interlocks with a protrusion 80 provided on the frame attachingportion 64. This arrangement interlocks the sealing portion 66 to theframe attaching portion 64. However, the sealing portion 66 may becoupled to the frame attaching portion 64 in other suitable manners.

Alternatively, the entire connector 60 may be made of silicone or asilicone-like material with differing rigidity characteristics for thefirm frame attaching portion 64 and the flexible sealing portion 66. Forexample, as shown in FIG. 8A, the connector 60 may have a one-piececonstruction and the frame attaching portion 64 may have a cylindricalstructure adapted to sealingly engage the outlet 24 of the flowgenerator 20.

Preferably, the connector 60 has a round shape to provide minimalout-of-mold distortion. The face seal 72 of the flexible sealing portion66 has approximately 2 mm to 3 mm interference from the nominal contactpoint to ensure sufficient contact when the connector 60 is pushedagainst the inlet 54 of the humidifier tub 50. The aperture 74 in theface seal 72 may be larger than the inlet 54 of the tub 50 in order toaccommodate the various misalignment and manufacturing tolerances of theconnector 60 to outlet 24 of the flow generator 20, to ensure sufficientpassage of air flow through the connector 60.

Advantageously, the face seal 72 provides for tolerance in movement inall directions while aligning the humidifier tub 50 and the flowgenerator 20. For example, the face seal 72 is flexible axially(forwards and backwards), laterally (upwards, downwards, and/orsideways), angularly, pivotally, and/or rotationally. Preferably, theface seal is flexible in all directions, although it may be moreflexible in some but more rigid in others.

The face seal 72 may be flexible within a predetermined range. Forexample, the face seal 72 may be axially and/or laterally flexiblewithin a range of about 1-5 mm, preferably about 2-3 mm. However, theface seal 72 may be axially and/or laterally flexible less than 1 mm orgreater than 5 mm. Also, the face seal 72 may be angularly, pivotally,and/or rotationally flexible within a range of about 1-10°, preferablyabout 3-6° or about 5°. However, the face seal 72 may be angularly,pivotally, and/or rotationally flexible less than 1° or greater than10°.

In use, the firm frame attaching portion 64 of the connector 60 issecurely attached to the outlet 24 of the flow generator 20 and thebellows-type conforming face seal 72 on the flexible sealing portion 66protrudes therefrom. The air inlet 54 of the humidifier tub 50 ispositioned adjacent to or abutting the face seal 72. When pressurizedair flows out through the outlet 24 of the flow generator 20, the faceseal 72 fills with air and establishes a pressurized face seal with theinlet 54 of the humidifier tub 50.

FIGS. 8B and 8C illustrate an embodiment of the connector 60 forming aseal with the inlet 54 of a humidifier tub. As shown in FIG. 8B, theconnector 60 is positioned adjacent the inlet 54 such that thebellows-type conforming face seal 72 is spaced from the inlet 54. Aspressurized air flows out through the outlet of the flow generator (asindicated by the arrow), the face seal 72 fills with air and expandsinto engagement with the axial end or axially facing surface of theinlet 54 as shown in FIG. 8C. That is, the face seal 72 balloonsoutwardly to form a cylindrical face seal with the inlet 54.

The bellows-type conforming face seal 72 provides a flexible bellows orgusset that allows the face seal 72 to self align with the inlet 54.That is, the flexibility and freedom of movement of the face seal 72(e.g., in all directions within a predetermined range) allows the faceseal 72 to form a seal with the inlet 54 even if they are misaligned.Specifically, the face seal 72 can still form a seal with the inlet 54even if the axis of the connector 60 is not aligned with the axis of theinlet 54. This arrangement accommodates the various misalignments thatmay occur between the connector 60 and the inlet 54.

Although the connector 60 has been described as being attached to theoutlet 24 of the flow generator 20, in an alternative embodiment theconnector 60 may be attached to the inlet 54 of the humidifier tub 50and the flexible sealing portion 66 may abut the outlet 24 of the flowgenerator 20. In a further embodiment, the connector 60 may bepermanently attached to either the outlet 24 of the flow generator 20 orthe inlet 54 of the humidifier tub 50. However, the connector 60 ispreferably a separate component that can be easily replaced or removedfor cleaning or sterilization purposes.

4.0 Mechanism for Retaining Humidifier in Cradle

The CPAP device 10 may include a cradle (e.g., cradle 40 in FIGS. 9-12)structured to support the humidifier tub 50 in an operative positionwith respect to the flow generator 20. The cradle may include a frontwall 114, side walls 116 and a heater plate that includes a heatingelement, e.g., a ceramic heating element. In use, the cradle receivesthe humidifier tub 50 so that the heating element is in thermal contactwith the heat conducting base plate 52 (FIG. 3) of the humidifier tub50. This arrangement allows water contained within the humidifier tub 50to be heated to provide sufficient moisture to the air so that patientswill be comfortable. In addition, the front wall 114 of the cradle facesthe rear wall 112 of the humidifier tub 50 when the humidifier tub 50 isdocked within the cradle 40. Also, the side walls 116 of the cradle 40are configured to face the generally planar side walls 102 of thehumidifier tub 50 such that the humidifier tub 50 is properly alignedwith respect to the cradle 40 as the humidifier tub 50 is slid in theassembly direction (FIGS. 9-12 and 23-26).

The cradle may provide one or more of the following functional featuresfor the humidifier tub 50: allow the humidifier tub 50 to be correctlyoriented with respect to the flow generator 20; securely lock thehumidifier tub 50 within the cradle such that it cannot be easily pulledout during use; ensure good thermal contact between the humidifier tub50 and the heater plate present in the cradle; allow easy docking of thehumidifier tub 50, especially for frail, elderly users; and for safetyreasons, limit access to hot areas of the humidifier chamber when heatis being transferred from the heater plate to the heat conducting baseplate 52 of the humidifier tub 50, once the humidifier tub 50 is dockedwithin the cradle.

Advantageously, the cradle as described in the various embodimentsherein pushes the humidifier tub downwards onto a fixed heater platerather than forcing the heater plate upwards against the humidifier tub.The fixing of the hot plate in the cradle improves and simplifies theelectrical ensures that the hot plate is sealed against water entry,which sealing is more difficult if the hot plate is movably mounted onthe cradle. In this type of arrangement, a spring that forces thehumidifier tub into engagement with the heater plate may be disengagedduring installation of the humidifier tub within the cradle. Thedisengagement of the spring reduces friction forces for installationthus making installation easier and consequently minimizing frictiondamage to the heater plate, cradle, and humidifier tub. Afterinstallation of the humidifier tub, the spring may be reengaged tosimultaneously secure the humidifier tub within the cradle and force thebase plate of the humidifier tub against the heater plate to providegood thermal contact between them.

4.1 Cradle with Securing Catch

FIGS. 9-12 illustrate a cradle 40 according to an embodiment of thepresent invention. As illustrated, the cradle 40 has a securing catch 44that lifts up and down to enable release or insertion of the humidifiertub 50. The securing catch 44 may be hinged. The lifting up of thesecuring catch 44 also disables or releases a spring that pushes thehumidifier tub 50 down against the heater plate 42 (see FIGS. 9 and 10).After insertion of the humidifier tub 50 along the arms of the catch 44,closure of the catch 44 re-engages the spring to ensure a good thermalconnection between the humidifier tub 50 and the heater plate (see FIGS.11 and 12). Releasing the spring (e.g., by lifting the catch)substantially reduces the forces that have previously acted againstfreely inserting or removing the humidifier tub. The catch 44 also locksthe humidifier tub 50 within the cradle 40 such that it cannot be pulledout during use, e.g., by pulling the air delivery tube. Specifically, astop 46 is positioned in front of the humidifier tub 50 when the catch44 is closed to lock the humidifier tub in place. Also, the stop 46 mayprovide a ridge or protrusion 43 adapted to lock the catch 44 in aclosed position. In addition, a groove 45 may be provided in the stop 46to provide a finger access that facilitates access to the catch 44. Thecatch 44 also prevents access to the hot heater plate 42 when thehumidifier tub 50 is inserted, especially access to the front of the hotheat conducting base plate 52. The gaps between the sides of the tub andthe cradle are smaller than the size of a finger (or less) to preventaccidental burning of the patient. The catch provides a “clicking” soundwhen the tub is properly docked thereby providing audio/tactile feedbackto the patient.

4.2 Cradle with Sliding Docking Portion

FIG. 13 illustrates a cradle 240 according to another embodiment of thepresent invention. In this embodiment, the cradle 240 includes a dockingportion 244 that is slidable between a humidifier tub locking positionand a humidifier tub unlocking position (FIG. 13). The slidablemechanism may be similar to that used in loading a CD or DVD, forexample, and may include a spring to facilitate movement into thehumidifier tub unlocking position. In the humidifier tub unlockingposition as shown in FIG. 13, the docking portion 244 is slidablyextended from the cradle 240 to enable release or insertion of thehumidifier tub 50. In the humidifier tub locking position, the dockingportion 244 is slidably retracted into the cradle 240 to secure thehumidifier tub 50 to the cradle 240. In the illustrated embodiment, thedocking portion 244 includes a pin 241 that is adapted to releasablyengage a ramp 243 provided on the cradle 240 to releasably lock thedocking portion in the humidifier tub locking position. However, thedocking portion 244 may be locked in other suitable manners. Also, aspring-loaded arm 246 may be provided to ensure a good thermalconnection between the humidifier tub 50 and the heater plate of thecradle 240.

4.3 Cradle with Pivoting Docking Portion

FIGS. 14A, 14B, and 15 illustrate a cradle 640 according to anotherembodiment of the present invention. In this embodiment, the cradle 640includes a docking portion 644 that is pivotable about a hinge 641between a humidifier tub locking position (FIG. 14A) and a humidifiertub unlocking position (FIG. 14B). The cradle 640 includes a spring 648that biases the docking portion 644 into the humidifier tub lockingposition. In the humidifier tub unlocking position as shown in FIG. 14B,the docking portion 644 is pivoted downwardly against bias from thespring 648 to enable release or insertion of the humidifier tub 50. Inthe humidifier tub locking position as shown in FIG. 14A, the dockingportion 644 is pivoted upwardly by the spring 648 to secure thehumidifier tub 50 to the cradle 640. FIG. 15 is an isolated view of thedocking portion 644 and illustrates retaining members 645 that push downon the humidifier tub 50 (e.g., the lateral edges).

4.4 Cradle with Spring-Biased Clamping Edge

FIG. 16 illustrates a cradle 340 according to another embodiment of thepresent invention. In this embodiment, a lever or button (e.g., anactuator button 345) is provided on the cradle 340 that is adapted torelease a spring 344 connected with a clamping edge 346, e.g., apressure pad. In use, the humidifier tub 50 is inserted into the cradle340 and the lever or button is actuated to release the spring-biasedclamping edge 346 which clamps or frictionally secures the base of thehumidifier tub 50 between the cradle 340 and the clamping edge 346. Theclamping edge 346 provides downwardly directed pressure to ensure goodthermal contact between the base of the humidifier tub 50 and the heaterplate.

4.5 Cradle with Pivotable Front Guard and Pivotable Humidifier RetainingPortion

FIGS. 17-22 illustrate a cradle 440 according to another embodiment ofthe present invention. In this embodiment, the cradle 440 includes twoseparate hinges 443, 444 that allow independent movement of a frontguard 445 and a humidifier retaining portion 446, respectively. Thefront guard 445 is pushed or pivoted downwardly which in turn lifts thehumidifier retaining portion 446 so it can pivot in an upward direction(as shown in FIGS. 17, 20, and 22). This subsequently allows easyinsertion of the humidifier tub 50 into the humidifier retaining portion446. The humidifier retaining portion 446 has edges adapted to receivesides of the humidifier tub 50 therein. Once the humidifier tub 50 isinserted within the humidifier retaining portion 446, the front guard445 is released which allows both the front guard 445 and the humidifierretaining portion 446 to clasp the humidifier tub 50 and move thehumidifier tub downwardly against the heater plate of the cradle 440(see FIGS. 18, 19, and 21). Thus, the front guard 445 clamps thehumidifier retaining portion 446 in a closed position. In an embodiment,a spring provides a bias to force the front guard 445 and the humidifierretaining portion 446 into a closed or humidifier retaining position.

4.6 Cradle with Front Guard and Pressure Pads

FIGS. 23-27 illustrate a cradle 540 according to yet another embodimentof the present invention. In this embodiment, the cradle 540 includes afront guard or stop 544 and at least two pressure pads 546. In theillustrated embodiment, a pressure pad 546 is positioned on each side ofthe cradle 540 so that each pressure pad 546 is offset from a receivingside of the cradle 540 so that each side of the cradle includes aC-shaped channel adapted to slidingly receive a respective shoulder 104of the humidifier tub 50 with the ramped portions 108 being receivedbefore the main portions 106. A spring 545 is attached to each pressurepad 546. The spring 545 is configured to force the respective pressurepad 546 in a downward direction toward the bottom of the cradle 540. Thefront guard or stop 544 includes a spring that forces the front guard orstop 544 upwardly to protect against access to the cradle 540 andprevent the humidifier tub 50 from falling out when installed. Toinstall the humidifier tub 50 to the cradle 540, the front guard or stop544 is pushed downwardly, thereby allowing the humidifier tub 50 toaccess the cradle 540 (see FIG. 24). The shoulders 104 of the humidifiertub 50 are then inserted underneath each of the pressure pads 546thereby causing the pressure pads 546 to be deflected upwards againstbiasing of the springs 545. This allows the humidifier tub 50 to slideinto the cradle 540 (see FIGS. 25-27). Once the humidifier tub 50 islocated within the cradle 540, the pressure pads 546 supply the force tomaintain the base of the humidifier tub 50 against the heater plate 542.In addition, once the humidifier tub 50 is fully inserted in the cradle40, the front guard or stop 544 is moved vertically relative to thehumidifier tub 50, thereby preventing withdrawal of the humidifier tub50 in a direction opposite the installation direction (i.e., withdrawaldirection). In an embodiment, movement of the front guard or stop 544 iscoordinated with actuation of the pressure pads 546. Preferably, thepressure pads 546 are made of smooth material that provides low frictionagainst the humidifier tub 50 when it is inserted into the cradle 540.FIGS. 26 and 27 illustrate the humidifier tub 50 located within thecradle 540 and the inlet 54 of the humidifier tub 50 engaged with theconnector 60 shown in FIGS. 5-7.

4.7 Water Damage Mitigation

In addition to the protection afforded by the tub design, the flowgenerator also has one or more water damage mitigating features.

System goals: The combined system (the flow generator and humidifier)should be able to prevent water entry into the flow generator fromscenarios where the unit (flow generator and humidifier) is tipped up to60° in any direction (e.g., backwards or sidewards). Even though theflow generator and/or humidifier is ideally designed to prevent waterentry into the flow generator, the flow generator should be capable ofhandling spill-back (e.g., about 100 ml) from the humidifier. Spill-backcan occur if water is accidentally introduced directly via the outletport. The device should not be damaged, and remain safe, with 100 mlintroduced, assuming the device remains in the horizontal operatingposition. It should be possible to drain any such water that has enteredthe flow generator (contained within the Outlet Muffler/sump).Furthermore, the flow generator should satisfy the IPX1 ratingrequirements, and the requirements of IEC60601.1, to cope with externalspillage of water by user.

One or more of the above goals can be achieved by implementation of theillustrative flow generator design shown in FIG. 28. FIG. 28 shows aflow generator 600 having a top case 605 and a bottom case 610. Top case605 is provided with a keypad 615 that is operably coupled to a main PCB620 with SMPS. Bottom case 610 is provided with base rubber feet 625.Arrows 630 schematically show the approximate path of air as it flowsinto, through and out of the flow generator 600. The bottom case 610includes an inlet that directs incoming air to a motor chamber 635 thathouses a motor 636. The motor 636 pressurizes the air and directs it toa muffler (or sound muffler) 637 that provides acoustic noise reduction.From the muffler 637, the pressurized gas exits via a flow generator airoutlet (or flow generator air outlet port) 650 that is in communicationwith an air delivery conduit. Sound insulation materials 655 may beprovided, but these are preferably outside the air path.

The ability to cope with water intake at the flow generator air outlet650 is achieved in this example by having the muffler 637 actessentially as a water sump/pump, where water cannot reach theelectronics or the motor unless the device is intentionally tipped overand/or tilted backwards.

Water that has entered the flow generator 600, and is contained in themuffler 637, can be drained by tilting the flow generator forward forwater to exit the air delivery port. The flow generator air outlet 650of flow generator 600 is arranged such that when the device is tippedforward it is the lowest point of the volume where water is trapped.Otherwise, the water will simply evaporate over time.

Other water mitigation features include the following features, each ofwhich can be used alone or in combination with one or more of the otherfeatures:

Mounting the blower air inlet downwards, allowing spill back from theHumidifier to drain out of the blower inlet (into the Fan Cover) andaway from the motor;

Having a very large volume (essentially the vacant space of bottomcase—much larger than 100 ml) outside of and lower than the blower, sothat water spill back has to completely fill this chamber before it canreach the motor;

Placing all electronics at the top of the device well away from internalwater; and/or

Placing the electrical interfaces (all cable connections includingpower) not only high on the device but above the air inlet opening wherespilled water could enter the device.

For IPX1 and IEC60601.1 tests, sealing should be provided on the jointsbetween keypad 615 and top case 605. Top case 605 shrouding 606 may alsobe constructed to form an “awning” over the power inlet and humidifiercommunications sockets. The joint between the top and bottom cases isdesigned to be noise tight.

The geometry of the flow generator layout is such that the sump chamberof the muffler 637 and the flow generator air outlet port 650 are notaxially aligned with a motor outlet 660. As shown in FIG. 28, the motoroutlet 660 directs the pressurized gas to a fitting 665 that is incommunication with the chamber. The fitting 665 is formed as part of, oris otherwise provided to a gasket seal 670 that follows the contour ofthe chamber. While the lower portion of the seal 670 contacts thechamber, the upper portion of the seal contacts a cover member orportion 675 that may be integrally formed with the blower outlet, etc.

As schematically shown in FIG. 29, the axis 680 of the motor outlet 660is offset from the axis 685 of the chamber outlet 690 and/or bloweroutlet 695. Thus, any water that enters the chamber from the humidifierwill not be directly channeled to the motor outlet 660.

In an alternative shown in FIG. 30, the axis 680 of the motor outlet 660can be aligned with the axis 700 of the chamber/blower outlet 690, 695,yet any water from the humidifier is not directly channeled to the motoroutlet 660 because a chamber 705 is formed on a lower part of aconnecting tube 710 that connects the motor outlet to the flow generatoroutlet. The tube has inlet and outlet portions 715, 720. The chamber 705is provided to store a volume of water that may be accidentallyintroduced into the flow generator from the humidifier. This water willevaporate and/or will be reintroduced into the air path to add extrahumidity, or the water can simply be emptied out by tilting or by use ofa drain. The arrangement in FIG. 30 can be used in the flow generatorshown in, for example, FIG. 14 of US patent application publication no.US 2005/0103339 A1, incorporated herein by reference in its entirety.

While the invention has been described in connection with what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the invention. Also, the various embodiments described abovemay be implemented in conjunction with other embodiments, e.g., aspectsof one embodiment may be combined with aspects of another embodiment torealize yet other embodiments. In addition, while the invention hasparticular application to patients who suffer from OSA, it is to beappreciated that patients who suffer from other illnesses (e.g.,congestive heart failure, diabetes, morbid obesity, stroke, barriatricsurgery, etc.) can derive benefit from the above teachings. Moreover,the above teachings have applicability with patients and non-patientsalike in non-medical applications.

What is claimed is:
 1. A positive airway pressure device configured todeliver a pressurized flow of respiratory gas to a patient's airways,the positive airway pressure device comprising: a flow generatorcomprising a blower configured to pressurize the flow of respiratory gasand a blower wall with a blower discharge path configured to convey thepressurized flow of respiratory gas from the blower; a flexible faceseal connected to the blower wall, the flexible face seal comprising anaperture and a lip curling inwardly from a perimeter of the flexibleface seal toward the aperture; a tub configured to hold a body of waterand humidify the pressurized flow of respiratory gas, the tub comprisinga heat conducting base plate and a tub side wall, the tub side wallhaving a substantially flat portion that surrounds an air opening thatis substantially co-planar with the substantially flat portion; a basethat supports both the flow generator and the tub and comprises a floorwith a heater plate, the tub being removable from the base by moving thetub in a first direction and being receivable by the base by moving thetub in a second direction opposite the first direction to engage theflexible face seal; and a guide assembly comprising a pair of flangeportions and a pair of C-shaped channel portions, each of the C-shapedchannel portions being configured to receive a respective one of thepair of flange portions, wherein the heater plate of the base ispositioned to engage the heat conducting base plate of the tub when thetub is received by the base, wherein the substantially flat portion ofthe side wall that surrounds the air opening of the tub is arranged toengage the lip of the flexible face seal upon the tub being fullyreceived by the base, wherein the tub and the flexible face seal areconfigured so that no part of the tub enters the aperture of theflexible face seal when the tub is fully received by the base, whereinthe base is configured so that the tub is automatically secured on thebase when the tub fully slides into place and contacts with flexibleface seal, and wherein the tub is configured to be released from thebase by way of pressing down on a resiliently biased surface.
 2. Thepositive airway pressure device of claim 1, further comprising asecuring catch configured to releasably retain the tub on the base, thesecuring catch being pivotable and being configured to produce aclicking sound when the tub is fully received by the base.
 3. Thepositive airway pressure device of claim 1, wherein the tub furthercomprises a conduit configured to convey the pressurized flow ofrespiratory gas from the air opening of the tub to an interior of thetub.
 4. The positive airway pressure device of claim 1, wherein theflexible face seal comprises an elastomeric portion that includes thelip and comprises a rigid portion that is a permanent part of the blowerdischarge path, the rigid portion being plastic and the elastomericportion being silicone.
 5. The positive airway pressure device of claim1, wherein the flow generator further comprises a housing and theentirety of the blower discharge path is within the flow generatorhousing.
 6. The positive airway pressure device of claim 1, wherein thelip of the flexible face seal is configured to be pressed against thetub side wall when the flexible face seal is pressurized.
 7. Thepositive airway pressure device of claim 1, wherein each of the C-shapedchannel portions is positioned so that a bottom part of the C-shapedchannel portion is lower than the heat conducting base plate of the tubwhen the tub is laterally received by the base, and wherein each of theC-shaped channel portions comprises a vertical wall that laterallyextends in a direction that is parallel to the direction in which thetub is received by the base.
 8. The positive airway pressure device ofclaim 1, wherein the resiliently biased surface comprises a groove, andthe tub is configured to be released from the base by way of pressingdown on the groove.
 9. The positive airway pressure device of claim 1,wherein the flow generator is separable from the base.
 10. The positiveairway pressure device of claim 1, further comprising a securing catchconfigured to releasably retain the tub on the base, wherein thesecuring catch is pivotable, wherein the tub further comprises a conduitconfigured to convey the pressurized flow of respiratory gas from theair opening of the tub to an interior of the tub, wherein the flexibleface seal comprises an elastomeric portion that includes the lip andcomprises a rigid portion that is a permanent part of the blowerdischarge path, wherein the rigid portion of the flexible face seal isplastic and the elastomeric portion of the flexible face seal issilicone, wherein the flow generator further comprises a housing and theentirety of the blower discharge path is within the flow generatorhousing, wherein the lip of the flexible face seal is configured to bepressed against the tub side wall when the flexible face seal ispressurized, wherein each of the C-shaped channel portions is positionedso that a bottom part of the C-shaped channel portion is lower than theheat conducting base plate of the tub when the tub is laterally receivedby the base, and wherein each of the C-shaped channel portions comprisesa vertical wall that laterally extends in a direction that is parallelto the direction in which the tub is received by the base.
 11. Thepositive airway pressure device of claim 1, wherein the tub isconfigured to separate from the flexible face seal upon being removedfrom the base.
 12. The positive airway pressure device of claim 1,further comprising: a securing catch assembly comprising a first springand being configured to secure the tub within the base upon the tubbeing fully received by the base, the securing catch assembly furthercomprising a catch and a manually depressable portion that is downwardlypressable against the bias of the first spring to move the catch from asecuring position, in which the tub is secured against horizontalmovement relative to the base, to a release position in which the tub ishorizontally slidable to remove the tub from the base; and a secondspring configured to bias the heater plate towards the heat conductingbase plate, the first and second springs being different from oneanother.
 13. The positive airway pressure device of claim 1, wherein theflexible face seal is positioned at an outlet end of the blowerdischarge path, wherein the air opening is an inlet air opening, whereinthe tub is horizontally removable from the base by sliding the tub awayfrom the blower wall and is horizontally receivable by sliding the basetoward the blower wall, wherein the guide assembly is configured toprevent the tub from being removed from the base in a verticaldirection, and wherein the C-shaped channel portions oppose each otherand each of the C-shaped channel portions comprises an open side thatfaces the other C-shaped channel portion.
 14. A positive airway pressuretreatment system comprising: the positive airway pressure device ofclaim 1; and an air delivery tube, wherein the positive airway pressuredevice further comprises an air delivery tube connector configured to beconnected to the air delivery tube.
 15. The positive airway pressuretreatment system of claim 14, further comprising a patient interfacethat is connectable to the air delivery tube.
 16. A positive airwaypressure device configured to deliver a pressurized flow of respiratorygas to a patient's airways, the positive airway pressure CPAP devicecomprising: a flow generator portion comprising a blower configured topressurize the flow of respiratory gas, a blower discharge pathconfigured to convey the pressurized flow of respiratory gas from theblower, and a flexible face seal positioned at an outlet end of theblower discharge path, the flexible face seal comprising an aperture anda lip curling inwardly from a perimeter of the flexible face seal towardthe aperture; a humidifier portion configured to humidify thepressurized flow of respiratory gas, the humidifier portion and the flowgenerator portion sharing a common base, the humidifier portioncomprising a heater plate; a tub configured to hold a body of water, thetub comprising a heat conducting base plate and a side wall, the sidewall having a substantially flat portion that surrounds an air inletopening, the air inlet opening being substantially co-planar with thesubstantially flat portion; and a securing catch assembly comprising afirst spring and being configured to secure the tub within thehumidifier portion upon the tub being fully received by the humidifierportion, the securing catch assembly having a catch and a manuallydepressable portion that is downwardly pressable against the bias of thefirst spring to move the catch from a securing position, in which thetub is secured against horizontal movement relative to the base, to arelease position in which the tub is removable from the base, whereinthe heater plate of the humidifier portion is positioned to engage theheat conducting base plate of the tub when the tub is received by thehumidifier portion, wherein the substantially flat portion of the sidewall that surrounds the air inlet opening of the tub is arranged toengage the lip of the flexible face seal upon the tub being fullyreceived by the humidifier portion, and wherein the tub and the flexibleface seal are configured so that no part of the tub enters the apertureof the flexible face seal when the tub is fully received by thehumidifier portion.
 17. The positive airway pressure device of claim 16,further comprising a second spring configured to bias the heater platetowards the heat conducting base plate, the first and second springsbeing different from one another.
 18. The positive airway pressuredevice of claim 16, wherein the tub further comprises an air outlet, abase, a top part connected to the base, and a conduit configured toconvey the pressurized flow of respiratory gas from the air inletopening of the tub to an interior of the tub, and wherein the air inletopening and the air outlet are formed on the top part of the tub. 19.The positive airway pressure device of claim 16, further comprising aguide that prevents the tub from being removed from the humidifierportion in a vertical direction, the guide comprising at least oneC-shaped channel portion, each said C-shaped channel portion comprisingan inwardly facing open side.
 20. The positive airway pressure device ofclaim 16, wherein the securing catch assembly is pivotable.
 21. Thepositive airway pressure device of claim 16, wherein the flexible faceseal comprises an elastomeric portion that includes the lip andcomprises a rigid portion that is a permanent part of the blowerdischarge path.
 22. The positive airway pressure device of claim 21,wherein the rigid portion of the flexible face seal is plastic and theelastomeric portion of the flexible face seal is silicone.
 23. Thepositive airway pressure device of claim 16, wherein the flow generatorportion further comprises a housing and the entirety of the blowerdischarge path is within the housing.
 24. The positive airway pressuredevice of claim 16, wherein the lip of the flexible face seal isconfigured to be pressed against the side wall of the tub when theflexible face seal is pressurized.
 25. The positive airway pressuredevice of claim 16, wherein the flow generator portion is separable fromthe humidifier portion.
 26. The positive airway pressure device of claim16, further comprising: a guide that prevents the tub from being removedfrom the humidifier portion in a vertical direction, the guidecomprising at least one C-shaped channel portion, each said C-shapedchannel portion comprising an inwardly facing open side; and a secondspring configured to bias the heater plate towards the heat conductingbase plate, the first and second springs being different from oneanother, wherein the tub further comprises: an air outlet; a base; a toppart connected to the base; and a conduit configured to convey thepressurized flow of respiratory gas from the air inlet opening of thetub to an interior of the tub, wherein the air inlet opening and the airoutlet are formed on the top part of the tub, wherein the securing catchassembly is pivotable, wherein the flexible face seal comprises anelastomeric portion that includes the lip and comprises a rigid portionthat is a permanent part of the blower discharge path, wherein the rigidportion of the flexible face seal is plastic and the elastomeric portionof the flexible face seal is silicone, wherein the flow generatorportion further comprises a housing and the entirety of the blowerdischarge path is within the housing, and wherein the lip of theflexible face seal is configured to be pressed against the side wall ofthe tub when the flexible face seal is pressurized.
 27. The positiveairway pressure device of claim 16, wherein the tub is secured againsthorizontal movement relative to the base, to a release position in whichthe tub is horizontally slidable to remove the tub from the base. 28.The positive airway pressure device of claim 16, wherein the tub isconfigured to separate from the flexible face seal upon being removedfrom the base.
 29. A positive airway pressure treatment systemcomprising: the positive airway pressure device of claim 16; and an airdelivery tube, wherein the positive airway pressure device furthercomprises an air delivery tube connector configured to be connected tothe air delivery tube.
 30. The positive airway pressure treatment systemof claim 29, further comprising a patient interface that is connectableto the air delivery tube.